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Proceedings of the Royal Society of Edinburgh. [Sess. 
II. — The Effect of a Meat Diet on Fertility and Lactation. By 
B. P. Watson, M.D., F.R.C.S.E. ( From the Physiological 
Laboratory, University of Edinburgh.) Communicated by Pro- 
fessor Schafer, F.R.S. (With a Plate.) 
(MS. received November 21, 1906. Read December 3, 1906.) 
In a paper on “ The Influence of Diet on Growth and Nutrition,” in the 
Journal of Physiology (vol. xxxiv., p. iii), Dr Chalmers Watson showed 
that in rats a diet of ox-flesh begun when the animals were weaned inter- 
fered with the development of pregnancy, none of the four flesh-fed 
animals having young, whereas the control animals from the same litter 
all became pregnant. On the other hand, it is stated of three families fed 
on horse-flesh from the age of 2J months approximately, that all became 
pregnant, from which he concludes that “ the use of this diet in animals of 
this age appears not to affect the supervention of pregnancy.” 
It was further found in the case of the meat-fed animals which became 
pregnant and suckled their young that the mammary tissue was less 
developed than in the control bread-and-milk-fed rats. 
At Dr Chalmers Watson’s suggestion I have extended these observa- 
tions, and with a larger amount of material at my disposal am able to 
amplify his statements, and as regards the question of fertility slightly to 
modify them. 
The method of conducting the investigation was as follows -.—Twelve 
female rats and several males were put on a bread-and-milk diet, and the 
females were continued on this throughout pregnancy and lactation. These 
served as the controls. Seventeen females and five males were put upon 
an ox-flesh diet, but were otherwise under exactly the same conditions as 
the bread-and-milk animals. The animals were begun on the meat diet at 
various ages, from the second up to the fourth month, and some of them 
were kept on the diet for as long as five months. 
1. Effect of a Meat Diet on Fertility. — Of the 17 animals fed upon a 
meat diet only 8 became pregnant, and of these 4 bore young within 21 
days — the usual gestation period in the rat — of being put on the diet, so 
that only 4 actually conceived while on the diet. Of these latter one had 
been 24, one 25, one 27, and one 30 days on an exclusive ox-flesh regimen. 
The other 9 animals, although kept for several months, did not conceive, 
and this in spite of the fact that they were seen to copulate freely right 
